Events at Physics |
Events on Thursday, May 8th, 2008
- R. G. Herb Condensed Matter Seminar
- Force-Producing Machines in Living Cells
- Time: 10:00 am
- Place: 5310 Chamberlin
- Speaker: Ben OShaughnessy, Columbia University
- Abstract: Living cells exert force in many basic processes. Forces cleave the mother cell into two daughters during cytokinesis in cell division, enable rigidity sensing in cell growth and differentiation, apply traction during cell migration and stimulate extracellular matrix reorganization during wound healing. For these and many other purposes cells assemble and operate complex multiprotein cytoskeletal machines. I will discuss assembly and function of contractile cellular machines built from actin filaments, force-producing myosin motor proteins and other components. (1) How are these machines assembled? We studied the contractile cytokinetic ring in fission yeast using time-resolved quantitative confocal microscopy and computer simulations. Assembly occurs via a remarkably stochastic "search, capture, pull and release" mechanism whereby ~63 membrane-bound precursor nodes are condensed into a continuous ring when node-bound myosins pull on transient formin-nucleated node-node actin connectors. (2) How do the machines work? We discuss stress fibers, possibly the most accessible cellular contractile force-producing machines. We quantitatively modeled their kinetics as dramatically revealed by two recent experimental studies.
- Host: Joynt
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- The South Pole Telescope: Beyond Clusters
- Time: 4:00 pm
- Place: 4274 Chamberlin
- Speaker: Tom Crawford, University of Chicago
- Abstract: The 10-meter South Pole Telescope (SPT) is currently operating at the National Science Foundation South Pole research station. The first-generation receiver on the SPT is a 960-element array of bolometers operating near the background limit to their sensitivity. The first key project, currently underway, is a survey of <1000 square degrees for galaxy clusters using the Sunyaev-Zel'dovich Effect (SZE), which will have sufficient statistical weight to place significant constraints on the equation of state of the dark energy. But the science yield of this survey will not be limited to the cluster catalog: This SPT dataset will provide precise measurements of the small-scale angular power spectra of primary cosmic microwave background (CMB) anisotropies, the thermal Sunyaev-Zel'dovich Effect (SZE), and the kinetic SZE / Ostriker-Vishniac effect; measurements of lensing of the CMB by clusters and large-scale structure; and catalogs of high-redshift starburst galaxies and active galactic nuclei with depth and sky coverage unprecedented at millimeter wavelengths.